Prevalence of Vitamin D Inadequacy in Athletes
Written by Ben Bunting: BA, PGCert. (Sport & Exercise Nutrition) // British Army Physical Training Instructor // S&C Coach.
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Vitamin D deficiency can negatively impact skeletal muscle function, athletic performance and body composition. However, there is a lack of prospective studies investigating the effects of vitamin D supplementation on sports performance and musculoskeletal function.
A 2019 study investigated the prevalence of vitamin D inadequacy among healthy male athletes living in Kuwait. The research team assessed serum 25(OH)D concentrations, anthropometric measurements and lifestyle questionnaires to identify potential risk factors.
Vitamin D
Vitamin D is a fat-soluble sterol nutrient that plays an essential role in immune function, protein synthesis, hormone synthesis, bone growth and repair, cell turnover and regeneration. It is synthesized in the skin and produced by exposure to sunlight for 15-30 min or absorbed from fatty fish, egg yolk, dairy products and fortified foods.
Athletes are at risk of vitamin D deficiency due to increased utilisation and storage depletion compared with non-athletes. Vitamin D deficiency is particularly common in power sport athletes (65.4%) compared to endurance sport athletes (32.9%), possibly related to vitamin D utilisation and reserve in skeletal muscles.
In general, athletes need a combination of dietary intake, sunlight exposure and supplementation to achieve sufficient serum 25(OH)D level for optimal athletic performance, and to prevent the development of vitamin D deficiency in winter months. Ideally, a serum 25(OH)D level should be measured at least twice yearly in athletes screened ‘at-risk’: once in the early spring for the nadir and once in late summer for a peak level.
One study aimed to investigate the prevalence of vitamin D inadequacy among athletes (power and endurance) using a cross-sectional approach. It will also examine the relationship between serum 25(OH)D levels and maximal oxygen uptake (VO2max).
The prevalence of vitamin D inadequacy was determined by comparing the serum 25(OH)D level in players in 2018 (n=23) and 2020 (n=24). All participants were men and consented to participate in the study.
Results showed a significantly higher prevalence of vitamin D inadequacy in power sports (n=23) than in endurance sports (n=24) at both the winter and spring periods. This may be related to the fact that a significant reduction in access to sunlight was experienced by all participants during the COVID-19 hiatus, which negatively affected vitamin D utilisation and storage in their skeletal muscle.
This suggests that the COVID-19 pandemic impacts vitamin D utilisation and storage in athletes and that this may negatively impact athletic performance. Further research on the association between serum 25(OH)D levels and performance is needed. Moreover, the importance of regular screening for vitamin D inadequacy needs to be reinforced and recommended.
Research
Vitamin D is essential for the maintenance of human musculoskeletal function. It is synthesised in the body through exposure to sunlight and is obtained from food sources such as oily fish, egg yolks, fortified milk and dairy products. Insufficient serum 25-hydroxyvitamin D concentrations (25 nmol/L) have been linked to an increased risk of osteoporosis and rickets, decreased bone mineral density, and impaired physical performance.
However, the prevalence of vitamin D inadequacy among athletes is not well understood. There are several factors that may contribute to vitamin D deficiency in athletes, including sun exposure, diet and age. In addition, dietary deficiencies, lack of awareness about vitamin D, and the use of vitamin D supplements can lead to low levels of serum 25-hydroxyvitamin D.
This is a global problem, especially for people living in areas with limited sun exposure and who consume minimal amounts of vitamin D from dietary sources. Athletes should be encouraged to increase their intake of foods that are rich in vitamin D, such as fatty fish and eggs.
The aforementione 2019 study aimed to assess the prevalence of vitamin D inadequacy in athletes, and to investigate whether there is a relationship between the level of vitamin D in their blood and their physical performance. We used a 'gold standard' method of measurement, liquid chromatography-tandem mass spectrometry (LC-MS/MS), to determine the concentrations of 25-hydroxyvitamin D in blood samples from 116 male athletes from 15 different outdoor and indoor sports.
Athletes were recruited from universities and sports facilities in Kuwait. Detailed information about their demographics was collected, including gender, age and sport activity. During Ramadan, the participants were also asked to provide their serum 25-hydroxyvitamin D concentrations, as well as dietary vitamin D intake.
The results showed that there was a significant increase in the prevalence of vitamin D inadequacy after Ramadan, with a mean concentration of 8.7% at baseline and 11.4% after Ramadan. Athletes with vitamin D inadequacy had a lower maximal aerobic power than those who were not deficient in 25-hydroxyvitamin D, although there was no statistically significant difference in a submaximal exercise test. These findings highlight the importance of ensuring a reliable and valid measure of serum 25-hydroxyvitamin D in order to determine the prevalance of vitamin D inadequacy in sports.
Are Athletes Deficient in Vitamin D?
Prevalence of vitamin D inadequacy in athletes is high, with a majority of individuals having concentrations below 20 ng/mL. A large percentage of sports-related injuries are associated with vitamin D deficiency and have prompted research into the effects of vitamin D on muscle function, performance, and injury prevention.
Athletes with a vitamin D insufficiency are at an increased risk of musculoskeletal injuries and decreased performance, particularly during cold weather periods. They are also at greater risk for developing stress fractures. Several studies have found that a higher serum 25-hydroxyvitamin D (25(OH)D) concentration is associated with lower rates of musculoskeletal injuries.
To assess the impact of vitamin D supplementation on total 25-hydroxyvitamin D (25(OH)D) levels in highly trained athletes, a dose-response study was conducted. Blood samples were collected at baseline from male and female athletes (18-32 years). The athletes were then randomly assigned to one of three groups. They were given 400, 1100 or 2200 IU of vitamin D3 daily for 12 months.
At the end of the study, both the had significantly higher serum 25(OH)D concentrations than the group receiving no supplements. The 2200 IU group had an increase in their total 25(OH)D concentration of +50+-27 nmol/l, whereas the 1100 IU group had an increase of +4+-17 nmol/l.
Despite the substantial effect of supplementation, a number of factors remain to be addressed before vitamin D supplementation can be considered as a safe and effective means of improving athletic performance in athletes. These include assay variability, a lack of sample comparability and a need for appropriate statistical power analysis to draw meaningful correlations.
A large number of athletes have a deficiency in vitamin D, and the prevalence is increasing as athletes are exposed to less sunlight. Therefore, the need for reliable cut-off values for providing a safe intake guidance to athletes is imperative. Furthermore, the prevalence of vitamin D insufficiency is similar among athletes of different types of sports, ranging from endurance and power sports to indoor and outdoor sports.
Conclusions
Vitamin D inadequacy is a common problem that can result from a lack of sun exposure or from avoiding sun exposure to the skin. Fortunately, many people can increase their levels of vitamin D through supplementation.
Low vitamin D levels have been linked to a variety of diseases and conditions, including cancer, cardiovascular disease, muscle deterioration, stress fractures, immune deficiencies, and autoimmune disorders. Athletes are particularly at risk for vitamin D deficiency because of their increased dietary intake and training schedules.
Athletes should make it a priority to obtain regular blood tests for their vitamin D levels. Ideally, these tests should be done at least twice a year to measure nadir and peak levels.
The prevalence of vitamin D inadequacy among athletes varies widely. For example, studies of power sports have shown higher prevalences than endurance sport.
Some factors can make it more difficult to increase vitamin D levels. For example, people who are obese or overweight have more fat to store in their bodies, which prevents vitamin D from being absorbed into the body.
Similarly, some areas of the world do not get sufficient sunlight during the winter months, which can also reduce an athlete’s intake of vitamin D. In addition, some athletes use sunscreen or other methods to protect their skin from the sun.
In addition, there are a number of other factors that can influence an athlete’s vitamin D levels. For example, some athletes travel to higher latitudes for training and competition, which limits their sun exposure.
There is a growing body of research that shows that vitamin D deficiency can lead to poor performance and even death in some cases. It has also been linked to inflammation, which can cause injuries and illness. Therefore, it is essential that all athletes receive adequate vitamin D to improve their overall health and performance.
